Numerous types of machines have been intended for use in the pulverizing and dispersion of granular material. Japanese Publication of Unexamined Patent Application KOKAI Number SHO58-17851 describes one capable of pulverizing granular material to sub-micron size.
This apparatus is equipped with a housing containing a cylindrical inner surface, the inside of which housing contains a shaft driven by a motor, a set of driving plates fixed to the shaft, a shaft with the flexibility of a cable fixed to the two driving plates and parallel to the above-mentioned shaft, and a rotor assembly consisting of three rollers which revolve freely in relation to the above driving plates.
When the motor causes the shaft to revolve mainly by the centrifugal force generated by the revolution of the rotor assembly in conjunction with the shaft, the flexible shaft will bend, and each roller will be pressed against the inner surface of the housing while revolving in the opposite direction from that of the shaft. This mechanism effects processes such as pulverization by grinding the granular materials between the rollers and the inner surface of the housing.
In the rollers of the above-mentioned apparatus spiral grooves are cut, and these spiral grooves convey processing materials from the top of the driving plates downward. However, when the apparatus is used to pulverize particles, as shown in FIG. 8, a large particle may become caught between one of the convex portions (102) of the outer surface of the roller (101) and the inner surface (103) of the housing. In such a case, compressive and shearing forces are not applied to the particles which are located between the other convex portions (102) and the inner surface (103) of the housing. In addition, force is not applied to the particles located in the spiral grooves (104). As a result, the outer surface (102) of the roller (101) does not function effectively.
Even if the outer surface (102) of the roller (101) is finished sufficiently flat so that it comes into close contact with the inner surface (103) of the housing, extended periods of normal use or short period of use with highly abrasive granular material will cause the convex portion (102) of the aforementioned roller (101) to wear out and its shape to change. As a result, the whole surface will not function effectively.
Moreover, in the above apparatus, since the method of mounting roller (101) to the flexible shaft is very complicated, highly skilled labor has been required to replace it. Cleaning the apparatus by disassembling it has been also difficult, and replacing roller (101) is a specialized task. Manufacturing roller (101) has also been very labor-intensive, so the apparatus has been very expensive.